1. Technical Field
The present invention relates to a technology for automatically adjusting the focus of an imaging device.
2. Related Art
Some of conventional stationary cameras have the function of presetting various parameters representing the user's arbitrary settings, for example, a pan position, a tilt position, and a zoom magnification. The imaging direction of the stationary camera having this function is quickly changeable by simply reading out these preset parameters. After the change of the imaging direction, the position of a focus lens is adjusted to focus the camera on a subject.
Latest cameras generally have the auto focusing function to automatically adjust the focus. A typically adopted auto focusing control technique is hill-climbing control that moves a focus lens in a lens unit to maximize an evaluation value calculated from a high frequency component of a luminance value of a captured image (see, for example, Japanese Patent Laid-Open No. H07-87377 and No. H01-125065).
The hill-climbing control requires a relatively complicated series of processing to analyze the captured image with moving the focus lens, calculate the evaluation value from the high frequency component of the analyzed image, and detect the maximum of the calculated evaluation value. The hill-climbing control thus takes a relatively long processing time. Although the image direction of the camera is quickly changeable according to the preset parameters, the subsequent hill-climbing control takes time to adjust the position of the focus lens. The user may thus be uncomfortable with a response delay.